Refrigerated container for liquefied gases

ABSTRACT

781,631. Storing gases under pressure. UNION CARBIDE &amp; CARBON CORPORATION. Aug. 22, 1955 [Sept. 10, 1954], No. 24159/55. Class 8(2). A liquefied gas, e.g. oxygen container 11 mounted within and thermally insulated from a jacket 12 through which extends a filling and discharge tube 22 has a refrigerant container 28 in thermal contact with the liquid oxygen L ; the refrigerant being capable of change of state, e.g., from solid to liquid accompanied by absorption of heat at a temperature above the normal storage temperature of the liquid oxygen but below that at which the gas pressure is sufficient to open an automatic relief valve 25. A suitable refrigerant is dichlorodifluoromethane which is introduced as liquid through a duct 29 closed by a burstable disc 30. The container 28 is supported by braces 31 and container 11 by a tripod 16 within the jacket 12 which may be evacuated or filled with insulation. Charging with liquid oxygen is effected through the valved duct 22 until liquid issued from a trycock valve 27 and discharging is also effected through the duct 22 leading to a line 33 where it is joined by oxygen gas in a duct 40 connected to a gas release duct 24. The combined liquid and gaseous oxygen then traverses a vaporizing coil 35 surrounding the jacket 12 and is discharged as gas through a valved coupling 38. Alternatively the vapourizing coil is located within the jacket 12. In a modification the refrigerant is of the evaporative type, e.g. liquid nitrogen for use with argon in the container 11; the burstable disc being replaced by an automatic pressure relief valve 44&lt;SP&gt;1&lt;/SP&gt;, Fig. 3 (not shown).

May 13, 1958 P. E. LOVEDAY REFRIGERATED CONTAINER FOR L'IQUEFIED GASES Filed Sept. 10, 1954 2 Sheets-Sheet 1 INVENTOR PAUL E LOVEDAY BY 5 ATT RNEY May 13, 1958 P. E. LOVEDAY REFRIGERATED CONTAINER FOR LIQUEFIED GASES Filed Sept. 10, 1954 2 Sheets-Sheet 2 '&-%\ 4 INVENTOR PAUL E. LOVEDAY ATTORNEY United rates Patent 2,834,187 REFRIGERATED COPigER non 'LIQUEFIED Paul E. Loveday, Kenmore, N. Y., assignor to Union Carbide Corporation, a corporation of New York Application September 10, 1954, Serial No. 455,194 9 Claims. Cl. 62-1 This invention relates to improvements in containers for handling and storing low temperature commercial products, such as liquefied gases having boiling points below 233 K. at atmospheric pressure, and more particularly concerns containers for liquefied gases, such as oxygen, nitrogen or argon.

In the past, several difliculties have been encountered in the delivery of low temperature, liquefied gas containers to small users who .desire to use the gas in the gaseous state. One of the most important of thesedifiiculties concerns the vaporization and loss of oxygen from liquid oxygen containers as aresultofheatleakage such as might occur over periods of no demand or shutdown of the gaseous oxygen consuming operation.

For example, in the conventional double walled liquid oxygen container, the heat energy absorbedby the liquid oxygen as a result of heatleakage throughthecontainer walls is manifested by an increase inthe temperature of the liquid oxygen body, and also an increase in the oxygen gas pressurecorresponding to that increased temperature. in effect, this action createsexcessivepressure conditions within the oxy-gencontainer which heretofore could only be alleviated by an oxygenrelease valve,-wit h a consequent loss of gaseous oxygen tothe atmosphere.

To the end that the above .set forth diificulty may be avoided, there is provided herein an improved liquid container, wherein an auxiliary refrigerationconserving system is used in conjunction with the liquidoxygenstorage ssytem, and wherein the refrigerant used in .such system is effective in attenuating any rise in tempera ture and pressure within the oxygen container by absorbing heat from the liquid oxygen, as by the melt-ingor vaporization of'the refrigerant, within the rangepf liquid oxygenternperatures to be encountered during shut-down.

It is, therefore, an important objector the-presentinvention to provide a container for valuabie liquefied gas products, the container being capable ofstorin-g such products for comparatively long periods of no withdrawal from the container without loss of ,material through vaporization.

A further object of the present invention-is toprovide a novel container for holding liquefied gases, such as oxygen, argon or the like, ,andhaving an auxiliary refrigeration system so constructed and arranged as to decrease the rate of vaporization of the liquefied .gas due to heat leakage, and consequently reduce the rate. of increase in gas pressure in the container, thereby to effect longer periods of storage of such liquefiedgases with the development of only moderate pressures. 7

Still another object of the'present invention is-to-proofavacuum pump .valveoutlet 19 in the closure vide equipment for warmingliquid or gaseous oxygen issuing from the liquid oxygen container before ,itreaches its point of use, so that gaseous oxygen at a suitabletemperature and pressure Wi1l;be available for use.

Yet another object of the present invention is to .provide a portable liquid container which is ;relatively; light in weight and easily handled, small in; size, and. efiicient in operation.

Other i c srfe re an va age o tth ppte qn invention ,will be readily ,apparent from -the-jr'gllovgjng 2,834,187 Patented May 13, 1958 detailed description of certain embodiments thereof taken in conjunction with the accompanying drawings, in which:

Fig. 1 is a vertical sectional view of an exemplary container illustrating the principles and novel features of this invention;

Fig. 2 is a sectional view of the apparatus shown in Fig. 1 taken along the line 2-2;

Fig. 3 is a partial sectional view of a container similar-to Fig. 1, but showing a modified auxiliary refrigeration compartment fill pipe;

Fig. 4 is a partial sectional view of a container similar to Fig. 1, but showing a modified inner vessel fill line; and

Fig. 5 is a sectional view similar to Fig. 1, but showing a modified cold converter or superheater unit construction.

;In :Fig. 1 is shown a gas material holding container or double walled cylinder ltl embodying features of the persent invention. By the term gas material .is meant a low temperature product, such as oxygen, in the solid, liquid or gaseous state. The cylinder ltlimay be of more or less conventional construction for stationary or .portable use of the type having an elongated receptacle or inner pressure vessel 11 of impervious metal which is not .ernbrittled at low temperatures, such as stainless steel, for holding liquefied gas material, preferably .oxygen, and having normal liquid and gas spaces, L and .G, therein. The inner vessel 11 is surrounded by a larger gas-tight shell or jacket 12 of suitable metal material, for example, carbon steel, completely encompassing the inner vessel, and providing anlintervening evacuable insulating space 13 to provide substantial resistancetd heat leakage therethrough. Any suitable means torsuppdirting and centering the inner vessel 11 in the jacket 12lmay be used, an example of one embodiment being illustrated -in;Fig. l.

The jacket 12 includes a neck portion 14Iwhich supports the .inner vessel 11 by a vacuum-sealing closure :15 constructed of metal, preferably of bronze .or brass plate. The inner vessel 11 may be centered and held against side sway by means of a three legged support or tripod 16 having a central guide .opening'17 for receiving therethrough a vertical pin 18 attached to the lower wall of the vessel 11.

:The intervening space 13 may beevacuatedby means (not shown) attached .to a' vacuum 15, or thespace may be filled with thermal insulation through an opening in the iacket wall and capped by a metalsealing disc 20 made of"brass,.or the space may preferablybe'filled with a comminuted insulating material and evacuated to reduce heat leakage from the outside to the body of liquid oxygen in the vessel 11.

1 The absolute pressure within the intervening space 13 may be further reduced and maintained at a low value by attaching an adsorbent container 21 havingtherein a noncombustible adsorbent material, preferably silica gel, or a synthetic zeolite of the type des'cribe d by Robert Milton in U. S. applications Serial Numbers 400,385 and400,3 88, both filed December2 4, 1953,15 the lower outer surface of the inner vessel 11 for removing air: and water traces. h i W i T" Mean's are providedfor'filling or replenishing the supply of liquid oxygen in the inner vesseh and foi' discharging liquid therefrom. As illustrated, such "means coinpi'ise a suitable liquid phase pipe 22, controlled at its upper end by ,a fill valve 23. The pipe 2 PIfrablY extends throughsuitable gas-tight openings, in the closure nates lin ithe For the purpose of relieving any excessive gas pressures that may develop in the inner vessel 11, a gas phase pressure relief pipe 24 formed of a metal possessinghigh strength and relatively low heat conductivity, such as stainless steel, in communication with the gas space G in the inner cylinder 11 is connected gas tightly through the upper wall of said vessel. This relief pipe projects upwardly through an appropriate gas-tight opening in the closure plate 15. The outer end of the relief pipe 24 terminates in a pressure relief valve 25, which may be preset to open when a specified pressure condition obtains in the vessel 11 to allow gaseous oxygen to escape into the atmosphere.

The inner vessel 11 is customarily filled with liquid oxygen to the proper liquid level to form the usual proportionate liquid and gas spaces L and G. To ascertain when the liquid body has reached the desired level, the inner vessel is provided with a small diameter vent or trycock line 26 constructed of stainless steel pipe or like material, and passing through gas-tight openings in the inner vessel 11 and the sealing plate 15. This trycock line 25 has a trycoclr valve 27 at its outer end for exposing the line to atmospheric pressure. The other end of the trycock line 26 communicates with the inside of the liquid oxygen vessel, preferably disposed with its lower end portion extending down into the normal gas space G, but terminating slightly below the normal liquidgas line. Thus in the process of filling the inner vessel, as the liquid level reaches the lower end of the trycock line 26, the liquid oxygen will be forced upwardly into the trycock line by the oxygen vapor pressure Within the gas space G, and escape into the atmosphere and through the open trycock valve 27.

This allows the operator or attendant suilicient time to shut elf the supply of liquid oxygen, and stop the filling operation at approximately the desired liquid level.

As an alternative method of filling the inner vessel 11, the trycock line 26 may be replaced with suitable vent means, and the inner vessel filled by means of weight differential. Thus, by simply placing the cylinder to be filled on a preset scale balance and filling the cylinder until the scale balance indicates completion of the filling operation, a quick and convenient means for replenishing or filling the cylinder may be consummated. This method is preferred as it eliminates the trycock valve 27.

The modification shown in Fig. 4 shows a practical arrangement that might be used in filling the inner vessel 11 according to the weight differential method. In lieu of the trycock line 26 and relief pipe 2 the pipe 22 is constructed within a vent pipe 26 which functions in the capacity of a vent line. The pipe 22 extends into the liquid space L and reaches the bottom of the inner vessel 11, but the vent pipe 26 extends slightly into the gas space G at the top of the inner vessel 11. In charging the inner vessel 11, liquid oxygen is admitted through a charging connector line 27' into the pipe 22. A fill valve 23' in the charging connector line 27 controls the flow of supply liquid oxygen into the inner vessel 11, and a vent or relief valve 25 at the upper end of the vent pipe 26' allows vapors to escape as the vessel is being filled.

It is generally known that the loss of oxygen due to heat leakage from liquid cylinders of small capacity is an important factor to be considered in the distribution of liquid oxygen to small customers. Because of this, shutdown or no demand periods lasting two or three days will result in a rise in the temperature of the liquid oxygen confined in the liquid cylinder Ill, 21 rise in the saturation pressure of the confined gaseous oxygen, and eventually escape of gaseous oxygen from the inner vessel 11 when the oxygen gas pressure reaches the preset relief pressure of the relief valve 25 (or 25).

In accordance with this invention, means are provided for absorbing part of the sensible heat increase in the liquid oxygen cylinder due to heat leakageand thus retard the build-up of oxygen gas pressure to the extent that only moderate gas pressures will develop within the liquid cylinder over prolonged periods of non-use.

As a means for accomplishing this, I have provided an auxiliary refrigeration or heat storage system for conducting sensible heat away from the body of liquid oxygen and preventing, or to a considerable extent minimizing pressure build-up within the liquid cylinder over extended periods of no-demand. As shown in Fig. 1, an elongated refrigeration compartment 28 containing an auxiliary refrigerant is disposed in thermal association with the oxygen liquid and gas material confined therein and is preferably enclosed within the inner vessel 11, but it is to be understood that the refrigeration compartment 23 could also be formed as an annular refrigeration jacket disposed around the inner vessel in spaced relation to the outer shell 12, or in any other suitable relation permitting temperature equilibrium between the liquid oxygen and the refrigerant. For example, the refrigerant vessel may be positioned adjacent the liquefied gas holding vessel and have a metallic heat conducting path or paths between the refrigerant and the liquefied gas.

The auxiliary refrigeration system may be of the evaporative type, or may constitute a closed refrigeration system, the latter system being preferred and illustrated herein.

in a sealed refrigeration or heat storage system, it is desirable to use an auxiliary refrigerant having a reasonably low saturation pressure at ambient temperatures, so that it can be retained within its compartment without loss when it is warmed to the ambient temperature, a high latent heat of fusion or vaporization within the saturation temperature range of --166 C. to l45 C. expected to be encountered by the liquid oxygen, and a high specific heat capacity in the aforementioned liquid oxygen temperature range. I have found the refrigerant dichlorodifiuoromethane to be satisfactory, and suitable for use in the sealed auxiliary refrigeration system, since it has a melting point of l58 C., a saturation pressure of 130 p. s. i. g. at F., and an acceptable specific heat and heat of fusion.

It is to be understood that this invention is not limited to Freon-l2 as the auxiliary refrigerant, and that the choice of refrigerant is determined by the expected temperature operating range of the inner container 11.

As shown in Fig. 1, a connecting fill pipe 2i made of stainless steel or other suitable metal, is gas-tightly joined to an opening in the top of the refrigeration compartment, and extends outwardly through suitable gas-tight openings in the inner vessel 11 and the jacket closure plate 15. The refrigerant fill pipe line 2? outer end is connected to a sealing cap and bursting disk assembly 30.

The pipes 22 and 26 and the refrigeration compartment 23 are suitably braced against lateral movement within the inner cylinder 11 by one or more spider type reinforcement braces 31, two being illustrated in Fig. l. The pipes 22, 24 and 29 also function as suspension supports for the inner vessel and contents.

It is almost always necessary to supply oxygen at superatmospheric pressure, such as 50-l00 p. s. i. g., for customer consumption. To this end, the oxygen material from either the liquid phase line 22 or gas phase line 24 is passed through a conversion cycle apparatus which, when combined with the container, forms an apparatus known as a cold converter.

The conversion apparatus herein illustrated in Fig. l comprises a discharge line conduit 33, wliich'forms a T-junction 34 with the liquid phase line 22 located below the fill valve 23. The discharge line 33 runs downwardly in the form of a horizontal helical coil or conduit 35, enwrapped around the outer surface of the jacket 12, or suitably coiled adjacent the inner wall surface of the jacket, the former being shown in Fig. l by way of illustration, and the latter being depicted in Fig. 5. The latter is preferred to minimize the danger of helical as ets? .5 coil bfeak'age 'due to rough handling. The lower end of the helical conduit 35 then continues upwardly in a vertical run 35 having interposed near the end thereof a check valve 37, at the outer end of which is a service coupling 33.

The discharge lines 22 33, 35 and 36 absorb heat from'the atmosphere so that as the liquid oxygen passes therethrough, it is evaporated and superheated and ready for delivery at the conditions required for withdrawal by the consumer. I i

Provision is made for-selectively withdrawing gaseous oxygen from the inner container 11 into the helical conduit 35 to prevent excessive gas pressure build-up in said inner container. This is accomplished by a gas phase line 40 (Fig. '1) coupling the gas phase line 24 with the dischargeline 33 at T-junc'tures 41 and 42 respectively. interposed in the gas phase line 40 i's'a one- "way back pressure'valve'43 set at a predetermined pressure for example, open at 60p. is. i. g. and close at '50 p. 's. i. 'g. Thus, at all pressures above 60 p. s. i. g., withdrawal is gas phase to reduce inner container pressure, and at pressures below 50 p. s. i. g., withdrawal is liquid phase to prevent further reduction in inner container pressure.

In Fig. 4 is shown a cold converter apparatus substantially similar to that shown in Fig. l, the only difference'being in the specific manner of connection. Referring to Fig. 4,'discharge conduit 33 forms a T-juncture 34' with theliquid phase line 22, and the gas phaseline 40'is coupled to the vent line26' by'means of-a cross connector 41'. The liquid line 22 is brought out concentrically through the gas phase line 26 and through a sealing bushing of the cross 41'. The relief valve 25 is connected to the remaining lateral branch of the cross.

In operation, the action taking place within the con- .tainer over a two or three day periodof no withdrawal of oxygen material is "as follows:

Assume that withdrawal from the cylinder is stopped "for a three-day period with the liquidoxygen L initially at 50 p. ;s. i. g. and a saturation temperature of -166 C. Since substantial thermal equilibrium exists, the dichlorodifiuoromethane in the auxiliary refrigeration compartment 28 is also at l66 C. in the frozen state. As the sensible heat and pressure in the inner vessel 11 i'ncrease'due toheat leak, the warming liquid oxygen transfers heat to the frozen refrigerant as sensibleheat at r'isingtemperature. When theliquid oxygen and the dichlorodifluoromethane reach a temperature of about -1'58" C., the refrigerantstarts to melt. The liquid oxygen and Freon-1'2 then remain at the same temperature and pressure While the heat leak is absorbed as latent heatby the refrigerant until-thelatter is completely melted. The saturation pressure'of oxygen at l58'C.

"is95 p. s. i. g., which isappreciably lower than the oxygen relief valve setting. When the refrigerant'has completely changed toliqu'idphase, the liquid oxygen and dichlorodifluoromethane temperature and pressures resurne rising until the relief valve pressure is reached. 'Thus;'it is readily seen that asufiicient quantity of anxilia'r'y refrigerant with high heat capacity and-heat of fusion'eifectively reduces-thebuild-upof oxygen gas pressure'without .loss' of oxygen to theatmosphere which would otherwise occur during prolonged periods of no- "demand.

"Itisto be noted that on'resumption-of gaseousoxygen withdrawal after a period of no WithdraWaL the back pressure valve 43 is open to provide gas withdrawal from the gas space G so that pressure in'the inner cylinder 11 is reduced, causing further liquid oxygen vaporization When the dichlorodifluoromethane teman evaporat'ive type refrigerant.

refreezing, the temperature and pressures remaining constant during the .refreezing period. On completion of the refreezing process, the dichlorodifluoromethane and oxygen temperature and pressures resume dropping until the oxygen pressure reaches a set point at which back pressure valve 43 closes, and preferential liquid oxygen withdrawal commences, the temperature and pressures then remaining substantially constant. Thus, the auxiliary refrigerants capacity to further impede the increase in oxygen gas pressure over extended periods of nornwithdra is restored.

It is to be understood that while I have illustrated and described a sealedauxiliary refrigeration system, the auxiliary compartment could also be adapated for use with such a situation, the compartment 28 of Fig. 3 may be filled with an evaporative'type' refrigerant, such as liquid oxygen, liquid nitrogen, or liquid air, and the bursting disk assembly 44 be'replaced with a refrigerant relief valve 44.

In the modification shown in Fig. '3, the pipe 29 is provided with a concentrically disposed valve controlled tube 29' for supplying refrigerant liquid to the compartment 28, and the pipe 29 is terminated'at its upper end with a relief valve 44, as a means for venting the compartment as it is being filled, and for use as an automatic pressure releasing valve to maintain a desired erant system, the maximum argon pressure might be 225 vp. s. i. g., as limited by the setting of the product relief valve. To insure release of the nitrogen refrigerant be fore the valuable argon product, the refrigerant relief valve might be set at a pressure corresponding to an argon pressure of 210 p. s. i. g. The corresponding argon saturation temperature is 148 C., this temperature corresponding to a nitrogen saturation pressure of approximately 445 p. s.'i. g., which is the proper setting for the evaporative nitrogen refrigerant relief valve '44 (Fig. .3). Thus, upon the opening of the relief valve 44', the liquid nitrogen refrigerant would beeyaporated and-discharged to the atmosphere, and in so doing conduct heat at constant temperatureaway from .thefsurrounding liquid argon body in the inner vessel 11.

A principal requirement of this inventionis thatthe liquefied gas, product be kept in thermal equilibrium with the auxiliaryrefrigerant. This requirement must be met regardless of whether the refrigerant is of the sealed type illustrated in Fig. 1, or theevaporative typeillustrated in Fig. 3. While .the refrigerant compartment 11 is shown in contact with the "liquefied'gas productL, there are numerous types oflheat exchange equipment which can be employed to elfect temperature equilibrium between the product'and refrigerant. For example,

the, product and refrigerant vessels'could be adjacent each other and heat conducting paths of metal of high conductivity such as copper may'connect the vessels. The heat conducting paths may also. include metalffins orproiections extending into the liquid to aid in .maintaining temperature equilibrium between the product and thefref'rigerant. 'Whenan'evaporative refrigerant is used, the desired thermal equilibrium can be maintainedusually by regulating the pressurev in either or "both theproduct .and refrigerant compartments as determined'by'their relative .thermal properties. For example, liquid argon product at'Q p. s. i. g. can' be kept in fltherrnal equilibrium'with vaporizing nitrogen refrigerant at about 2 8 :p."s.'

pressure, thus preventing vaporization and loss of costly argon by atmospheric heat leak. On the other hand, if the refrigerant has a moderately higher boiling point than the liquefied gas product at one atmosphere pressure, the pressure on the product may be maintained at a higher value than the pressure on the refrigerant such that the refrigerant is preferentially evaporated to absorb the heat leak.

t will be understood that modifications and variations may be effected without departing from the scope of the novel concepts of the present invention.

What is claimed is:

1. In a system for storing liquefied gas material and dispensing gas therefrom, a thermally insulated pressure vessel for holding a supply of the liquefied gas under pressure, a refrigeration compartment in thermally conductive association with the liquefied gas in said vessel, and means for dispensing gas material at least from the gas phase of said vessel to a service connection under high pressure and temperature conditions occurring in i said vessel, said refrigeration compartment being sealed and having a non-consumable refrigerant characterized by a high latent heat of phase change within the temperature and pressure range of the liquefied gas in said vessel, for reducing the buildup in temperature and pressure in the liquid by absorption of heat during prolonged periods of non-dispensation, and for reducing the drop of pressure by supplying heat during periods of dispensing.

2. in a s stem for storing liquefied oxygen and dispensing oxygen gas therefrom, an inner vessel for holding a supply of liquefied oxygen, an air-tight outer vessel surrounding and supporting said inner vessel, and defining an cvacuable intervening space therebetween, a sealed refrigeration compartment in thermally conductive association with the liquid oxygen in said inner vessel, a liquid phase line outlet from said inner vessel operable to transfer liquid oxygen under pressure to a service dispensing means, a gas phase line outlet from said inner vessel operable to transfer gaseous oxygen under pressure to said service dispensing means, and a non-consumable refrigerant in said compartment for absorbing sensible heat from sai liquefied oxygen during storage periods without discharge of gasiiied material through said service dispensing means, and for giving up heat to said liquefied oxygen during oxygen dispensing periods, thereby conserving the useful gas material in said vessel.

3. A process for storing a low boiling liquefied gas material and dispensing gas therefrom according to claim 9, in which said gas material is oxygen and said refrigerant is dichlorodifiuoromethane.

4. A process for dispensing and storing low boiling liquefied gas material over prolonged periods of time, comprising introducing a supply of liquefied gas material into a closed, insulated vessel, where it is held in thermal association with a stationary refrigerant having a high latent heat capacity, absorbing a substantial portion of the sensible heat increase of said liquefied gas material in said refrigerant during prolonged storage periods to retard pressure increase and thereby avoid loss of gasified material through excess pressure gas relief, withdrawing liquefied gas from said vessel as required for use when the pressure therein is at a preselected operating pressure, selectively withdrawing gasified liquefied gas from said vessel when the gas pressure therein exceeds said preselected operating pressure, and transferring heat from said refrigerant to said gas material while said gasified liquefied gas is being withdrawn to prolong the period of gas withdrawal from said vessel.

5. In a system for dispensing and storing low boiling liquefied gas material having a closed vessel for holding a body of such liquefied gas at pressures below a selected upper limit pressure, a dispensing means connected to the "gas and liquid phase spaces of said vessel, and constructed and arranged for preferential dispensing withdrawal from the gas phase of said material in said gas and liquid phase spaces when the gas pressure in said vessel exceeds a desired operating pressure, and a heat insulating jacket surrounding said vessel; the combination therewith of a thermal storage unit disposed within said jacket and including a closed chamber containing a phase changeable material therein having a substantial latent heat capacity at temperatures within the range of the boiling point temperatures of said liquefied gas corresponding to said selected upper limit pressure and said operating pressure, said unit being adapted to absorb heat leaking through said jacket during periods of non-dispensation for substantially retarding the rise of pressure in said vessel and to transfer heat to said liquefied gas during a subsequent operation of said means for preferential withdrawal from the gas phase for regenerating the heat absorbing capacity of said material.

6. In a system according to claim 5, said phase changeable material being a liquid having a freezing point within said range.

7. In a system according to claim 5, wherein said liquefied gas is oxygen, and said phase changeable material is dichlorodifiuoroinethane.

8. In the art of storing a low boiling liquefied gas material in a closed vessel, and dispensing gas therefrom at a service pressure condition, the improvement of conserving the useful gas material in said vessel, comprising disposing a refrigerant in spaced and thermally conductive association with said gas material, insulating said refrigerant and gas material to retard the flaw of external heat thereto, maintaining a working pressure range in said vessel above said service pressure condition, utilizing as said refrigerant, a refrigerant material characterized by a high latent heat capacity due to a phase change at a temperature equal to a temperature of said gas material within said working pressure range, withdrawing gasified liquefied gas from said vessel when the working pressure has increased, and withdrawing liquefied gas from said vessel when said working pressure has decreased, whereby said refrigerant undergoes a phase change to absorb sensible heat from said gas material during the period of storage, and undergoes a reverse phase change to give off heat during the period of gas discharge.

9. In process for storing a low boiling liquefied gas material in a closed vessel and dispensing gas therefrom, the improvement comprising enclosing a body of a high latent heat capacity, phase-changeable refrigerant material in a refrigerant compartment in thermal association with said liquefied gas material, insulating said gas material and said refrigerant compartment to impede the flow of external heat therein toward the liquefied gas and refrigerant material, withdrawing gasified liquefied gas from said vessel when the pressure therein is above a preselected lower working pressure to a gas user, and Withdrawing liquefied gas from said vessel when the pressure therein is at said preselected lower working pressure, maintaining the pressure in said vessel between said preselected lower working pressure and a preselected higher working pressure to produce a heat ballast effect, whereby said refrigerant undergoes a phase change and acts to absorb sensible heat from said liquefied gas material during the period of storage, and undergoes a reverse phase change and acts to give off heat during the period of gas discharge.

References Cited in the file of this patent UNITED STATES PATENTS 1,773,140 Heylandt Aug. 16, 1930 2,148,109 Dana et al. Feb. 21, 1939 2,454,934 Mathis et al. Nov. 30, 1948 2,580,710 Wildhack Ian. 1, 1952 2,594,244 Winternitz Apr. 22, 1952 2,677,938 Loveday May 11, 195.4 

1. IN A SYSTEM FOR STORING LIQUEFIED GAS MATERIAL AND DISPENSING GAS THEREFROM, A THERMALLY INSULATED PRESSURE VESSEL FOR HOLDING A SUPPLY OF THE LIQUEFIED GAS UNDER PRESSURE, A REFRIGERATION COMPARTMENT IN THERMALLY CONDUCTIVE ASSOCIATION WITH THE LIQUEFIED GAS IN SAID VESSEL, AND MEANS FOR DISPENSING TAS MATERIAL AT LEAST FROM THE GAS PHASE OF SAID VESSEL TO A SERVICE CONNECTION UNDER HIGH PRESSURE AND TEMPERATURE CONDITIONS OCCURRING IN SAID VESSEL, SAID REFRIGERATION COMPARTMENT BEING SEALED AND HAVING A NON-CONSUMABLE REFRIGERANT CHARACTERIZED BY A HIGH LATENT HEAT OF PHASE CHANGE WITHIN THE TEMPERATURE AND PRESSURE RANGE OF THE LIQUEFIED GAS IN SAID VESSEL FOR REDUCING THE BUILDUP IN TEMPERATURE AND PRESSURE IN THE LIQUID BY ABSORPTION OF HEAT DURING PROLONGED PERIODS OF NON-DISPENSATION, AND FOR REDUCING THE DROP OF PRESSURE BY SUPPLYING HEAT DURING PERIODS OF DISPENSING. 